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This brief presents a low-power, area-efficient three-stage CMOS operational transconductance amplifier (OTA) suitable for very large capacitive loads, ${C} _{L}$ . A single Miller capacitor and an inverting current buffer embedded in the input stage are exploited to implement the frequency compensation network. An additional feed-forward path and a slew rate enhancer are also utilized to improve the large-signal transient response. Detailed small-signal analysis reveals that the proposed OTA does not exhibit an upper limit of drivable ${C} _{L}$ . The OTA is fabricated in a standard 0.35- ${\mu }\text{m}$ technology and occupies 0.0027 mm2 of die area. Under 1.4-V supply and 6.36- ${\mu }\text{A}$ quiescent current consumption, it provides a dc gain greater than 110 dB and is stable for any ${C} _{L}$ larger than 5 nF. Comparison with the state of the art shows remarkable improvement of both small- and large-signal performance.

The Muon Portal Project was born as a joint initiative between Italian research and industrial partners, aimed at the construction of a real-size working detector prototype to inspect the content of traveling containers by means of secondary cosmic-ray muon radiation and recognize potentially dangerous hidden materials. The tomographic image is obtained by reconstructing the incoming and outgoing muon trajectories when crossing the inspected volume, employing two tracker planes located above and below the container under inspection. In this paper, the design and development of the front-end electronics of the Muon Portal detector is presented, with particular emphasis being devoted to the photo-sensor devices detecting the scintillation light and to the read-out circuitry which is in charge of processing and digitizing the analog pulse signals. In addition, the remote control system, mechanical housing, and thermal cooling system of all structural blocks of the Muon Portal tracker are also discussed, demonstrating the effectiveness and functionality of the adopted design.

ASTRI-Horn is a prototypal telescope of an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF), proposed for the Cherenkov Telescope Array (CTA) Observatory. The CTA Observatory represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very highenergy domain from a few tens of GeV up to few hundreds of TeV. It will be composed of large-, medium-, and small sized telescopes; ASTRI-Horn is an end-to-end prototype proposed for the Small Sized array. The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon- Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system. This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented.

Within the framework of the Cherenkov Telescope Array (CTA) observatory, the Italian National Institute for Astrophysics (INAF) is leading the “Astrofisica con Specchi a Tecnologia Replicante Italiana” (ASTRI) Project mainly devoted to the definition and development of a set of small-size class telescopes with dual-mirror optical design (SST-2M) for the CTA southern site. The prototype of such telescopes, named ASTRI SST-2M, is installed in Italy at the INAF “M.C. Fracastoro” observing station located in Serra La Nave, Mount Etna, Sicily. In addition to the dual-mirror optical design based on the Schwarzschild-Couder configuration, the ASTRI SST-2M telescope adopts a focal plane camera formed by an array of monolithic silicon photomultiplier sensors coupled with a specifically designed front-end electronics and back-end electronics that represent a further innovative solution for the detection of atmospheric Cherenkov light. The ASTRI SST-2M prototype is currently under completion of the overall commissioning phase: structure, mirrors, camera, control software, data archiving and analysis pipeline. This contribution focuses the attention on the software devoted to the control and monitoring operations of the ASTRI camera. We will provide a brief description of the electronic assemblies and of the software architecture designed, according to software engineering modularization, in terms of functional blocks and how they are deployed in the back-end electronics. Then, we will show how all these functionalities are accessible by the user through the graphical user interface developed and currently used for the engineering tests performed on site.

This paper introduces a new effective single-Miller capacitor compensation topology for three-stage amplifiers with very large capacitive loads, realized through an active-feedback capacitor together with an inner half-feedforward stage. Moreover, an optimized design strategy which profitably exploits the two left half-plane zeros is presented. To improve the amplifier large signal transient response, the topology also includes an external feedforward path, that only marginally affects the frequency compensation, and a novel slew-rate enhancer section. To validate the solutions presented, a three-stage OTA driving a 10-nF load has been designed and implemented in a standard 0.35- $\mu\text{m}$ CMOS technology. The amplifier occupies less than 0.003-mm2 of die area, provides 2.7-MHz gain-bandwidth product and 0.55-V/ $\mu\text{s}$ average slew-rate, while consuming only 25- $\mu\text{A}$ quiescent current.

The design of a power-efficient three-stage CMOS operational amplifier capable of driving extremely high capacitive loads is proposed. The compensation network entails only a single Miller capacitor, thus avoiding the use of additional transistor and current consumption. Theoretical analysis is reported and an implementation in a 0.35-μm technology is presented and simulated. A 1.46-MHz gain-bandwidth product is achieved with a 10-nF load, while consuming only 8.54 μW from 1.4-V supply. As compared to other previously reported solutions, the amplifier shows a remarkable increase in small-signal and large-signal performance.

The Cherenkov Telescope Array (CTA) foresees, in its southern site (Chile), the implementation of up to 70 small-sized telescopes (SSTs), which will extend the energy coverage up to hundreds of TeV. It has been proposed that one of the first set of CTA SSTs will be represented by the ASTRI mini-array, which includes (at least) nine ASTRI telescopes. The endto-end prototype of such telescopes, named the ASTRI SST-2M, is installed in Italy and it is now completing the overall commissioning and entering the science verification phase. ASTRI telescopes are characterized by an optical system based on a dual-mirror Schwarzschild-Couder design and a camera at the focal plane composed of silicon photomultiplier sensors managed by a fast read-out electronics specifically designed. Based on a custom peak-detector mode, the ASTRI camera electronics is designed to perform Cherenkov signal detection, trigger generation, digital conversion of the signals and data transmission to the camera server. In this contribution we will describe the main features of the ASTRI camera, its performance and results obtained during the commissioning phase of the ASTRI SST-2M prototype in view of the ASTRI mini-array implementation.

The Muon Portal is a recently started Project aiming at the construction of a large area tracking detector that exploits the muon tomography technique to inspect the contents of traveling cargo containers. The detection planes will be made of plastic scintillator strips with embedded wavelength-shifting fibres. Special designed silicon photomultipliers will read the scintillation light transported by the fibres along the strips and a dedicated electronics will combine signals from different strips to reduce the overall number of channels, without loss of information. Different silicon photomultiplier prototypes, both with the p-on-n and n-on-p technologies, have been produced by STMicroelectronics during the last years. In this paper we present the main characteristics of the silicon photomultipliers designed for the Muon Portal Project and describe the setup and the procedure implemented for the characterization of these devices, giving some statistical results obtained from the test of a first batch of silicon photomultipliers.

Summary In this paper, we discuss a symbolic simplification methodology to derive approximated factorized forms of the transfer function of multistage amplifiers in the complex frequency domain. The developed approach is useful for hand calculation and is also suitable to be implemented in symbolic computer-aided design tools. Although the proposed methodology is mainly intended for the analysis and design of operational transconductance amplifiers, it can straightforwardly be applied to the small-signal analysis of any analog linear circuit. Design examples are provided to verify the effectiveness of the proposed approach implemented through a Matlab function. Copyright © 2015 John Wiley & Sons, Ltd.

This work addresses a systematic and in-depth electro-optical characterization of the Multi-Pixel Photon Counter (MPPC) sensors constituting the camera detection system at the focal plane of the ASTRI telescope prototype. The paper reports the experimental results of a large set of measurements on the MPPC devices in order to provide a reliable qualification of the detector performance and evaluate its compliance with the telescope focal plane requirements. In particular, breakdown voltage, internal gain, dark count rate, cross-talk and extra-charge probability, and absolute photon detection efficiency measurements are performed on the basic sensor device unit as a function of the detector operating conditions.

A comprehensive and in-depth characterization procedure for obtaining very accurate measurements on silicon photomultiplier detectors (SiPMs) is here described. A large amount of optical tests are systematically carried out and discussed in terms of the most important SiPM performance parameters; in particular, an accurate estimation of the photon detection efficiency in the 350-900-nm wavelength spectral range and in steps of 10 nm is achieved, based on the single-photon counting technique, with substraction of the dark noise contribution and avoiding the additional noise sources of crosstalk and afterpulsing. Some recently produced detectors are analyzed and their relevant electro-optical parameters are evaluated in order to demonstrate the effectiveness and efficacy of the adopted characterization procedure and data-handling protocols in assessing the overall SiPM performance, regardless of the specific device tested. Tests repeatibility is carefully verified and all the evaluated parameter trends are proved to be compatible with the physics theory of the SiPM device.

Cosmic ray tomography is a technique which exploits the multiple Coulomb scattering of highly penetrating cosmic ray-produced muons to perform non-destructive inspection of high-Z materials without the use of artificial radiation. A muon tomography detection system can be used as a portal monitor at border crossing points for detecting illegal targeted objects. The Muon Portal Project is a joint initiative between Italian research and industrial partners, aimed at the construction of a real size detector prototype (6×3×7 m 3 ) for the inspection of cargo containers by the muon scattering technique. The detector consists of four XY tracking planes, two placed above and two below the container to be inspected. After a research and development phase, which led to the choice and test of the individual components, the construction and installation of the detection modules is almost completed. In this paper the present status of the Project is reported, focusing on the design and construction phase, as well as on the preliminary results obtained with the first detection planes.

A high-performance buffer amplifier topology for liquid crystal display drivers is presented. The proposed amplifier achieves fast driving performance and offers a rail-to-rail common-mode input range. Enhanced slewing and settling capabilities are achieved through a novel output stage performing dual-path push-pull operation. No additional biasing network is required to set the quiescent conditions of the class-AB output stage, since the output static current is inherently controlled by the input differential stage itself, without additional power dissipation. Experimental results demonstrate that the suggested buffer can drive a 1000-pF capacitive load with a 5.7-V/μs slew-rate and a 0.71-μs settling time, while drawing 32-μA overall quiescent current from a 5-V power supply.

The present work aims to address a comprehensive analytical analysis of a new accurate equivalent electrical model of silicon photomultiplier (SiPM) detectors. The proposed circuit model allows to truthfully reproduce the output signal waveform generated by the light sensors apart from the specific technology adopted for the fabrication process, and can also be profitably exploited to perform reliable circuit-level simulations. A detailed and in-depth investigation of the functional parameters involved in the output pulse signals is here developed, and the most significant physical relationships are analytically derived as well. Experimental measurements are finally carried out on real devices, in order to validate the accuracy of the attained expressions, and good fittings are achieved between the analytical curve plots and the associated measurements results. The adopted analysis turns out to be particularly helpful when designing an optimum front-end architecture for SiPM detectors, since the performance of the entire detection system, especially in terms of dynamic range and timing resolution, can be accurately predicted as a function of the SiPM model parameters and the foremost features of the coupled front-end electronics.

In this paper, the traditional equivalent electrical model of silicon photomultipliers (SiPMs) is profitably extended to include the important effects of the read-out electronics on the shape of the output pulse waveforms. An improved analytical expression has been developed, which accurately reproduces the fast detector ignition, the avalanche self-quenching and the slow recharging operations, also taking into account both loading effect and bandwidth limitation of the coupled front-end. By means of the adopted analytical model, the SiPM dynamic response can be accurately mimicked and predicted, and reliable simulations can be also performed. Experimental tests on real detection systems corroborate the SiPM model and analytical results.

The present work introduces an improved SPICE equivalent electrical model of silicon photomultiplier (SiPM) detectors, in order to simulate and predict their transient response to avalanche triggering events. In particular, the developed circuit model provides a careful investigation of the magnitude and timing of the read-out signals and can therefore be exploited to perform reliable circuit-level simulations. The adopted modeling approach is strictly related to the physics of each basic microcell constituting the SiPM device, and allows the avalanche timing as well as the photodiode current and voltage to be accurately simulated. Predictive capabilities of the proposed model are demonstrated by means of experimental measurements on a real SiPM detector. Simulated and measured pulses are found to be in good agreement with the expected results.

In this letter, a recently published model of silicon photomultiplier (SiPM) sensors is profitably extended to include the important effects of the read-out electronics on the shape of the output pulse waveforms. An improved analytical expression has been developed, also accounting for the loading effect and bandwidth limitation of the coupled front-end, through which the SiPM dynamic response can be accurately reproduced and predicted. Experimental tests on actual detection systems corroborate the SiPM model and the analytical results.

Due to the recent advances in silicon photomultiplier technology, new types of Silicon Photomultiplier (SiPM), also named Multi-Pixel Photon Counter (MPPC) detectors have become recently available, demonstrating superior performance in terms of their most important electrical and optical parameters. This paper presents the latest characterization results of the novel Low Cross-Talk (LCT) MPPC families from Hamamatsu, where a noticeable fill-factor enhancement and cross-talk reduction is achieved. In addition, the newly adopted resin coating has been proven to yield improved photon detection capabilities in the 280–320 nm spectral range, making the new LCT MPPCs particularly suitable for emerging applications like Cherenkov Telescope Array, and Astroparticle Physics.

This paper presents the latest characterization results of a novel Low Cross-Talk (LCT) large-area (6×6-mm 2 ) Multi-Pixel Photon Counter (MPPC) detector manufactured by Hamamatsu, belonging to the recent LCT5 family and achieving a fill-factor enhancement and cross-talk reduction. In addition, the newly adopted resin coating is demonstrated to yield improved photon detection capabilities in the 290–350 nm spectral range, making the new LCT MPPC particularly suitable for emerging applications like Cherenkov Telescopes. For a 3×3-mm 2 version of the new MPPC under test, a comparative analysis of the large pixel pitch (75-µm) detector versus the smaller pixel pitch (50-µm) detector is also undertaken. Furthermore, measurements of the 6×6-mm 2 MPPC response versus the angle of incidence are provided for the characterized device.

The Cherenkov Imaging Telescope Integrated Read Out Chip, CITIROC, is the front-end chip of the camera for the ASTRI SST-2M, one of the prototypes for the small sized telescopes of the Cherenkov Telescope Array, CTA. The telescope, operating in the energy range from a few TeV to beyond 300 TeV, is characterized by innovative technological solutions. The optical system is arranged in a dual-mirror configuration and the focal plane camera consists of a matrix of multi-pixel Silicon Photo-Multipliers. Among others, one of the most important project issue consists in the thermal characterization of the camera that, in the ASTRI SST-2M prototype, is thermo-controlled in a narrow temperature range. A set of at least nine similar telescopes will form the ASTRI mini-array proposed to be installed at the CTA southern site. In the cameras of the ASTRI mini-array telescopes the thermal control could be relaxed with a considerable gain in terms of power consumption, cost and simplicity. So, a study of the temperature dependence of the camera components is needed. The present work addresses this issue showing the results of the measurements carried out on CITIROC as a function of the temperature. We focused our investigation on the pedestal stability, linearity of the charge output signal, preamplifier gain and trigger uniformity in the temperature range 15-30°C. Our results show, for each of the above-mentioned measurable quantities, that temperature dependency is at the level of a few percent.

ASTRI SST-2M is an Imaging Atmospheric Cherenkov Telescope (IACT) developed by the Italian National Institute of Astrophysics, INAF. It is the prototype of the ASTRI telescopes proposed to be installed at the southern site of the Cherenkov Telescope Array, CTA. The optical system of the ASTRI telescopes is based on a dual mirror configuration, an innovative solution for IACTs, and the focal plane of the camera is composed of silicon photo-multipliers (SiPM), a recently developed technology for light detection, that exhibit very fast response and an excellent single photoelectron resolution. The ASTRI camera electronics is specifically designed to directly interface the SiPM sensors, detecting the fast pulses produced by the Cherenkov flashes, managing the trigger generation, the digital conversion of the signals and the transmission of the data to an external camera server connected through a LAN. In this contribution we present the general architecture of the camera electronics developed for the ASTRI SST-2M prototype, with special emphasis to some innovative solutions.

Silicon photomultipliers (SiPMs) are emerging semiconductor-based photosensors, addressing the challenge of low-light detection down to the single-photon counting level. A design of high-performance front-end electronics for SiPM readout requires the development of accurate electrical models. Numerous SiPM reliable models have matured in recent years; however, circuit parameter extraction is rather cumbersome and involves extensive measurement steps to be performed. Starting from a recently developed model of the SiPM device coupled to the conditioning electronics, a new effective analytical procedure is, here, devised for extracting the SiPM model parameters from experimental measurements. The proposed extraction technique is applied to a $3\times 3$ -mm2 SiPM sensor, and is validated by comparing SPICE simulations and measurement results. Independent cross-check validation based on experimental tests corroborates the effectiveness of the adopted extraction procedure.